Ireland must beware Louis Picamoles' broadened horizons in Sunday's pivotal World Cup clash with France, according to Simon Easterby.

Forwards coach Easterby has warned Ireland to shut down power-runner Picamoles at source, admitting the Toulouse number eight will pose a significant threat at the Millennium Stadium.

Picamoles slipped out of form with France last year, but has fought his way back into favour, with Easterby crediting his Toulouse club-mate Imanol Harinordoquy for opening his eyes to an extra playmaking dimension.

Sunday's victors will top Pool D and draw Argentina rather than defending champions New Zealand in the quarter-finals, with Easterby calling on Ireland to deny France's thoroughbred forwards any room to run in Cardiff.

"Picamoles has always been dangerous as a ball carrier," said Easterby.

"He has the ability to knock players off if you go too high, and he also has ability to offload pretty well."

Veteran number eight Harinordoquy left home club Biarritz in 2014 after a decade's sterling service for one final move, to French Top 14 giants Toulouse.

The 35-year-old totem continues to excel across Europe's top contests, and Easterby believes his creative influence has rubbed off on Toulouse team-mate Picamoles amid his impressive renaissance.

"It obviously helps when you have someone like Harinordoquy playing alongside you," said Easterby.

"His experience for the French and Biarritz is exceptional. And I am sure his work rubs off on Picamoles.

"He along with a number of players in their pack have the ability to carry and offload.

"We have to trust what we do without the ball and make sure that we are on top of our game when we are defending.

"Every team has certain individuals who can break the game up and who will be more of a threat to the opposition.

"We have those players too. So we are on top of that.

"We have had a very good defensive day at training today, so we are heading in the right direction in terms of trying to negate what the French plan to do."